Metallurgical furnace



Sept. 16, 1941. H. 1 GENTIL 2,255,844

METALLURGICAL FURNACE Filed July l5, 1959 /1,\\ 2 INVENTOR.

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Patented Sept. 16, 1941 METALLURGICAL FURNACE HenriLouis Gentil, Paris, France, assigner to Societe dElectrochimie, dElectrometallurgie et des Acieries Electriques dUgine, Paris, France, a corporation of France Application July 13,1939, .Serial No. 284,293 In France January 14, 1938 (Cl. 26S-17) 2 Claims.

a furnace in which the extracting of volatileI metals may be conducted, under a vacuum, as a continuous operation.

A further object of the` invention is to provide areaction chamber supporting a high tem-v perature anda high degree of vacuum and of which however, the walls do not become wasted ,nor distorted in an abnormal manner, this chamber being so constructed that it may Work in a continuous manner.

One of the essentially few features of the improved metallurgical furnace is the fact that the inner and the outer surfaces of the heated retort or chamber which contains the materials under treatment are both submitted to a high vacuum, the said retort or chamber being to that purpose, enclosed in an outer receptacle submitted to the said Vacuum while the inside of the retort or` chamber is itself submitted to a high vacuum and preferably to the same degree of vacuum as the one of the retort or chamber. The wall of the outer receptacle can be maintained at a low temperature and the difference of the pressures between the atmospheric pressure and the high vacuum in the retort or chamber is entirely sustained by the Wall of the said outer receptacle' the same or about the same low pressure acting on both sides of the walls of the retort or inner chamber.

According also to the invention the furnace is provided with means to allow the feeding of the furnace, the continuous extraction of the volatile metal and the' elimination of dross without stopping the working of the furnace.

Again according to the invention the reaction retort or chamber of the furnace is eventually given a very flat shape and the materials to be 'treated are placed therein in a thin layer in order to hasten the reaction.

Again according to the invention an elongated retort or chamber may be used the two ends of the same being each connected with a condenser, means being provided for interrupting at will the communication between the retort or chamber and either of the condensers or with both. In a general manner, during the working of the furnace, one of the condensers is in communication with the furnace, for condensing the vapours of the volatilized extracted metal, the communication of the other condenser with the furnace being interrupted during this time, which allows the carrying off of the metal condensed herein.

The condenser for condensing the vapours of the volatilized extracted metal is eitherplaced inside the furnace or outside, and it is preferably cooled down to a temperature at which the metal cannot spontaneously take fire when put in contact with the atmosphere. -In the latter case it is easy to take the metal out of the condenser without 'stopping the heating of thel furnace.

Other features of the invention will appear from the detailed descriptionl given hereunder with reference to the accompanying drawing in which: l

Fig. 1 is adiametral section of an embodimentA of the invention corresponding to a vertical fur- I marce;

Fig. 2 is a-plan view of a section through 2-2 of the furnace illustrated in Fig. 1.

In the following description and claims the word chamber will be used for designating either a chamber or a retort.

As shown in Fig. 1 the furnace is a vertical one which comprises a chamber I the walls 6 of which are made of refractory material. The upper wall 4 is also constituted of refractory material and joined to the walls 6. .The chamber I has a very flat shape and two series of electrical resistances 2 are placed along the longest Walls of this chamber` throughout the height corresponding to the part of the chamber I in which there are reactant materials. The elec-iy tric current for the heating resistances 2 is led to the said resistances by conductors I1, 48. The

chamber I and heating coil 2 are surrounded by' denser is closed the chamber. Two condensers 9 can be respectively connected by means of valves 29 with conduits 130, leading to the chamber I. Both the :condensers 9 and the space 3 are connected by respective conduits I5, I6 provided with valves 3I1, I 9 and through a three-way cock 2| to a vacuum pump'I9 actuated by a` motor 20. 1 A special vacuumrelease valve I I is provided for each condenser, each condenser ls provided Y `with an outlet valve I4 which permits casting the liquid condensed metal into a receptacle I3. Each condenser is also provided with an appa- Aratus 36 which has plates 43 for the purpose oi?l .the condensation of the metallic vapours, directly in the solid state. This apparatus 36 is hung to a gas-tight cover 42 provided on the upper part of the condenser. 'Ihe valves 29 are actuated by means of rods 31 passingv L through the wall of the condenser', by means of a s'tufng-box 44. l A charging hopper 24, closed by a cover 25 and provided with a valve 23, is located at the top of chamber I for charging the furnace with the reacting materials and acts as a lock. A tight sluice 22 provides, under the valve 23, a chamber 40 acting as a sieve during the introduction of reacting material. 'I'his chamber 40 is provided with a conduit 46 connected with a vacuum pump. v

`vA crucible 3l is formed the chamber I at its bottom and a'valve 32 actuated by the rod or shaft 33 permits evacuating the dross from the chamber I. Under the crucible 3| there is provided a chamber 34 having a gas-tight wall 5, a gas-tight door 35 and a conduit 45 connected with a vacuum pump. It may be seen easily that by means of the pump I9, the same vacuum can be realized in the condensers' 9, the chamber I and the space 3. Thus the'part of the wall of the chamber I which is heated to high temperature is not submitted to a difference of pressure, the atmospheric pressure being totally sustained by the cool wall 1. In order to better insure a correct balance of the pressures on both faces of the wall 6 at its heated part, holes may be provided in said wall in the part referred to. Thus the wall 6 cannot be distorted. A further advantage is that the heat of chamber Ivcannot be conveyed'by convection to the outside'through 'the receptacle 3.

VThe furnace works as follows: the material to be treated `and which isfcapable of evolving a volatile metal, has been previously charged into f the chamber I by means of. the charging hopper 24, the tight sluice 22 and the valve 23 being opened. The left valve 29 is closed and the right valve 29 is opened, for.y instance, as shown in Fig.

, 1,. The left valve I1, the valve 23 and the tight sluice 22 are closed but the rightvalve I1 and the valve I8 are opened. The v alve II of the right condenser is closed and the pump I9 is set in motion. When a high vacuum is obtained in both the condenser 9 and the chamber I and the space 3 current is caused to pass in the heating coil 2. The reaction takes place in the material of chamber l, owing to the high heat developed; the volatile metal is liberated and vapourised. The metallic vapours so evolved are condensed in liquid form in the right condenser 9. When there is a sumcient quanti-ty of condensed metal in the right condenser the valve 29 of this conand the vacuum is. released in this condenser by opening the valve I I andclosing 7 n.. At the same time tnefvalves zo and n of the necessary to disconnect it.

Thus the liquid metal in the right-condenser can 'be tapped in the receptacle I3 through the valve other condenser by closing its'valves 29 and I1 after having connected the right condenser and so on. Obviously itis possible to leave the valves 29 of the two condensers opened. It is only when metal is carried off 'from a condenser that it is Itis possible to obtain directly crystallized solidied metal in the apparatus 3B provided with plates `43 by conducting'the operation in such a manner that the metallic vapour be, around these plates, under proper conditions-of temperature and pressure, viz those which are diierent of those of the triple point. For instance in case ofv aluminium there is directly condensation above the plates 43 in the solid state for a temperature of 1400 C. and a pressure of 2 mm. of mercury. The tight cover 42 provided in the upper part of thecondenser is opened and the appa'- ratus 36 charged with solid metal is carried off.

The operation may be conducted in a continuous way. There has already been described means for the continuous extraction of the metal obtained. When it is necessary. during the operation to charge new reactant material it is proin the chamber 4I),` equal to the vacuum of the chamber I, by means of the conduit 46. 'I'he tight sluice 22 isthen opened by means of the left condenser are opened and the valve I I closed'. 75

rod 39 and the. reacting materials are introduced into the chamber I.` The sluice 22 isclosed and the reactants have thus been introduced in the furnace. without practically any trouble in the working of the apparatus.

For the evacuatihg of the dross from the chamber I during the working of the apparatus, a

vacuum isl created in the chamber 34-equal to the vacuum ofthe chamber I, by 'means of the conduit 45. The valve 32 is then opened by-means of the shaft 33 ,and the dross falls 'down in the chamber 34. The valve 32 is' then closed, the tight door 35 is opened and the dross is evacuated 'without practically any trouble in the working oi' the apparatus. v

In the application of the apparatus, when treating for example aluminium ore by a' lreducing agent, e. g. iron-sulde, .the pressure in chamber I and in space'3 may be lowered down to 10-2 mm. of mercury land the temperature raised to 12001800 C. The liberated aluminium vapours condense in the condensers 9.

When the reactant i's in compact mass, which I is heated from the outside, the reaction occurs rst at the outside and after progressively in the ad inside of the mass, but very slowly. For instance,

when working at .the temperature of 1300 C. the

reaction has merely progressed for one centimeter from outside to inside of the mass for one hour operation. It is thus necessary to avoid to have a mass of reactants too heavy because the complete reaction be too slow. As it is preferable at'industrial point of view to work on important quantities of reactants the apparatus is elongated as shown in Fig. 2, the heating means being.

placed along the longest sides of the apparatus.

Various modifications .may be made in the device embodying the invention without departing from the spirit and scope thereof and all such modications are intended to be. covered by the appended claims. A

The same process may be applied to the closure for withdrawing What I claim is:

1. A metallurgical furnace comprising a closed reaction chamber having non-porous refractory walls, meansfor heating said reaction vchamber to a high temperature, a closed gas-tight receptacle surrounding the said reaction chamber, the space therebetween being filled with porous refractory material, a plurality of separate condensers located outside said receptacle but having gas-tight connection therewith, there being vfrom said reaction chamber to each of said conmaterial from said condensers, vacuum producing means and connections between said vacuum producing means and .said reaction chamber, said receptacle outside said reaction chamber and said condensers severally, the said connections to said condensers being valved, and said condensers each having a valved connection for relieving the vacuum there- 2. Apparatus as claimed in claim I in which the outlet from said reaction chamber is a valved outlet emptying into a chamber having a substantially gas-tight closure and a connection between said chamber and vacuum producing means. v

HENRI LOUIS GENTIL. 

